President Donald Trump has threatened to impose “serious tariffs” on the 27 member states of the European Union should he detect hostility behind the bloc’s offer to admit Canada as an associate member.

As the trade dispute between Toronto and Washington worsens, Prime Minister Mark Carney sought to ally with the EU.

“Canada’s been a terrible trade partner,” Mr Trump said at an airport in Charlotte, North Carolina. “If I think it’s at all a hostile act, I will put very serious tariffs or stop trading with Europe on many things.”

Mr Trump has repeatedly berated Canada over its refusal to accept proposed trade terms, which ultimately led to a tariff fallout between the two nations.

“Canada’s been a terrible trade partner,” Mr Trump told reporters at the airport in Charlotte, North Carolina. “If I think it’s at all a hostile act, I will put very serious tariffs or stop trading with Europe on many things.”

The U.S. president implied he could be open to the arrangement if he doesn’t sense an ulterior motive behind the offer.

“So, if they do that, if Europe does that, with a bad intention—if it’s a good intention, that’s fine—if it’s a bad intention, we’ll put very heavy tariffs on Europe,” he added.

European Commission president Ursula von der Leyen floated the possibility of allowing Canada to become the EU’s first associate member.

“I would like to work with you on opening the door for Canada to be the first associate member of the EU,” Ms von der Leyen said.